IDataParameter调用存储过程

public string  GenerateExamePaper(string paperType, string driverID, string MacAddr)
        {
            int i;
            IDataParameter[] iData = new SqlParameter[4];
            iData[0] = new SqlParameter("@paperType", paperType);
            iData[1] = new SqlParameter("@driverID", driverID);
            iData[2] = new SqlParameter("@MacAddr", MacAddr);
            iData[3] = new SqlParameter("@sReturn", SqlDbType.Char, 50, ParameterDirection.Output, false, 0, 0, string.Empty, DataRowVersion.Default,null);
            string aaa = "";
            i= DbHelperSQL.RunProcedureParOut("Pro_GenerateExamePaper", iData, out aaa).ToString();

            return aaa;

        }

  /// <summary>
        /// 运行存储过程，返回影响的行数
        /// </summary>
        /// <param name="storedProcName">存储过程名</param>
        /// <param name="parameters">存储过程參数</param>
        /// <param name="rowsAffected">影响的行数</param>

/// <param name="rowsAffected">返回output值</param>

        /// <returns></returns>
        public static int RunProcedure(string storedProcName, IDataParameter[] parameters, out int rowsAffected,out str)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                int result;
                connection.Open();
                SqlCommand command = BuildIntCommand(connection, storedProcName, parameters);
                rowsAffected = command.ExecuteNonQuery();
                result = (int)command.Parameters["ReturnValue"].Value;
              str= (int)command.Parameters["@sReturn"].Value;
                return result;
            }
        }